In a fuel cell, power generation performance is lowered in a case where the degree of wetness of an electrolyte membrane becomes too high or too low. In order to cause the fuel cell to effectively generate electric power, it is important to maintain the electrolyte membrane of the fuel cell at the proper degree of wetness.
JP2010-538415A discloses a fuel cell system in which the degree of wetness of a fuel cell is adjusted by controlling at least one of an anode gas flow rate and a cathode gas flow rate.